Experiments were carried out in a pilot scale CFB reactor with Meat and Bone Meal (MBM) blended with three coals. MBM has high Cl content, which produces fouling and corrosion in superheaters. Coal ash contains protective elements (Al, Si and S) that are able to trap alkalies, and the HCl that is released does not condense on superheaters. The goal of the study was to select the most protective coal so that the portion of MBM in the feedstock could be maximised. South African coal, with highest content of reactive aluminosilicate, provided more protection against chlorine deposition than did Polish and German coals. Alkali aluminosilicate formation was the main alkali sequestration path, dominating over sulfation.